The GDK manual says:
> A property has an associated format, an integer describing how many bits are in each unit of data inside the property. It must be 8, 16, or 32. When data is transferred between the server and client, if they are of different endianesses it will be byteswapped as necessary according to the format of the property.

It seems to mean that it should be interpreted as a string rather than a list of integers, but I'm not clear on that.